Hybrid interconnect for laser bonding using nanoporous metal tips

ABSTRACT

Embodiments relate to using nanoporous metal tips to establish connections between a first body and a second body. The first body is positioned relative to the second body to align contacts protruding from a first surface of the first body with electrodes protruding from a second surface of the second body. The second surface faces the first surface. The contacts, the electrodes, or both comprise nanoporous metal tips. A relative movement is made between the first body and the second body after positioning the first body to approach the first body to the second body. The contacts and the electrodes are bonded by melting and solidifying the nanoporous metal tips after approaching the first body and the second body.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/913,645 filed Oct. 10, 2019, which is incorporated by reference inits entirety.

FIELD OF THE INVENTION

This disclosure relates generally to micro light emitting diodes(micro-LEDs) for a display, and more specifically to establishing hybridinterconnections between micro-LEDs and control circuits in displaydevices using nanoporous metal tips.

BACKGROUND

Various types of light sources are used in many electronic displaydevices, such as televisions, computer monitors, laptop computers,tablets, smartphones, projection systems, and head-mounted devices(e.g., virtual reality (VR) devices, augmented reality (AR) devices,and/or mixed-reality (MR) devices). Modern displays may include wellover ten million individual light sources that may be arranged in rowsand columns on one or more backplanes. When assembling the display, itis typically required to electrically couple, bond, or affix (i.e.,establish an interconnection with) each of the light sources to thebackplane.

SUMMARY

Embodiments relate to a hybrid interconnection for laser bonding of afirst body to a second body using nanoporous metal tips. The first bodyhas a first surface with contacts protruding from the first surface. Thesecond body has a second surface with corresponding electrodesprotruding from the second surface. The second surface faces the firstsurface. The contacts, the electrodes, or both comprise nanoporous metaltips. The contacts bond with corresponding electrodes by melting andsolidifying the nanoporous metal tips.

Embodiments also relate to using nanoporous metal tips to establishconnections between a first body and a second body. The first body ispositioned relative to the second body to align contacts protruding froma first surface of the first body with electrodes protruding from asecond surface of the second body. The second surface faces the firstsurface. The contacts, the electrodes, or both comprise nanoporous metaltips. A relative movement is made between the first body and the secondbody after positioning the first body to approach the first body to thesecond body. The contacts and the electrodes are bonded by melting andsolidifying the nanoporous metal tips after approaching the first bodyand the second body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an artificial reality system including anear-eye display, in accordance with one or more embodiments.

FIG. 2 is a perspective view of a near-eye display in the form of ahead-mounted display (HMD) device, in accordance with one or moreembodiments.

FIG. 3 is a perspective view of a near-eye display in the form of a pairof glasses, in accordance with one or more embodiments.

FIG. 4 illustrates an optical see-through augmented reality systemincluding a waveguide display, in accordance with one or moreembodiments.

FIG. 5A illustrates an example of a near-eye display device including awaveguide display, in accordance with one or more embodiments.

FIG. 5B illustrates an example of a near-eye display device including awaveguide display, in accordance with one or more embodiments.

FIG. 6 illustrates an image source assembly in an augmented realitysystem, in accordance with one or more embodiments.

FIG. 7A illustrates a light emitting diode (LED) having a vertical mesastructure, in accordance with one or more embodiments.

FIG. 7B is a cross-sectional view of a LED having a parabolic mesastructure, in accordance with one or more embodiments.

FIG. 8A illustrates a method of die-to-wafer bonding for arrays of LEDs,in accordance with one or more embodiments.

FIG. 8B illustrates a method of wafer-to-wafer bonding for arrays ofLEDs, in accordance with one or more embodiments.

FIGS. 9A-9D illustrates a method of hybrid bonding for arrays of LEDs,in accordance with one or more embodiments.

FIG. 10 illustrates a LED array with secondary optical componentsfabricated thereon, in accordance with one or more embodiments.

FIGS. 11A and 11B are cross-sectional views of bonding contacts andelectrodes using nanoporous metal tips as a hybrid interconnect, inaccordance with one or more embodiments.

FIG. 12 is a flowchart illustrating a process for interconnecting afirst body to a second body via contact and electrodes using nanoporousmetal tips, in accordance with one or more embodiments.

The figures depict various embodiments for purposes of illustrationonly. One skilled in the art will readily recognize from the followingdiscussion that alternative embodiments of the structures and methodsillustrated herein may be employed without departing from the principlesdescribed herein.

DETAILED DESCRIPTION

Embodiments relate to a hybrid interconnection for bonding electrodeswith corresponding contacts using nanoporous metal tips. The contacts,the electrodes, or both have nanoporous metal tips. The contacts bondwith corresponding electrodes by melting and solidifying the nanoporousmetal tips. The contacts and/or the electrodes are heated so thatnanoporous metal at the tip may melt to have spherical surfaces. Byhaving the nanoporous metal located only at the tips of the contactsand/or the electrodes, the resulting interconnection after the laserbonding takes place between the contacts and the electrodes has lessvariations and reduces the likelihood of creating a short. For instance,a contact and/or electrode comprised of nanoporous metal (i.e.,nanoporous metal located throughout the entire contact and/or electrode)may convert from a cylindrical shape to a spherical droplet upon laserbonding. The volume and shape change may result in significant heightvariations that may lead to bonding failure (e.g., shorts or opens).

FIG. 1 is a block diagram of an artificial reality system 100 includinga near-eye display 120, in accordance with one or more embodiments. Theartificial reality system environment 100 shown in FIG. 1 may includethe near-eye display 120, an optional external imaging device 150, andan optional input/output interface 140, each of which may be coupled toan optional console 110. While FIG. 1 shows an example of the artificialreality system environment 100 including one near-eye display 120, oneexternal imaging device 150, and one input/output interface 140, anynumber of these components may be included in the artificial realitysystem environment 100, or any of the components may be omitted. Forexample, there may be multiple near-eye displays 120 monitored by one ormore external imaging devices 150 in communication with a console 110.In some configurations, the artificial reality system environment 100may not include the external imaging device 150, the optionalinput/output interface 140, and the optional console 110. In alternativeconfigurations, different or additional components may be included inthe artificial reality system environment 100.

The near-eye display 120 may be a head-mounted display that presentscontent to a user. Examples of content presented by the near-eye display120 include one or more of images, videos, audio, or any combinationthereof. In some embodiments, audio may be presented via an externaldevice (e.g., speakers and/or headphones) that receives audioinformation from the near-eye display 120, the console 110, or both, andpresents audio data based on the audio information. The near-eye display120 may include one or more rigid bodies, which may be rigidly ornon-rigidly coupled to each other. A rigid coupling between rigid bodiesmay cause the coupled rigid bodies to act as a single rigid entity. Anon-rigid coupling between rigid bodies may allow the rigid bodies tomove relative to each other. In various embodiments, the near-eyedisplay 120 may be implemented in any suitable form-factor, including apair of glasses. Some embodiments of the near-eye display 120 arefurther described below with respect to FIGS. 2 and 3. Additionally, invarious embodiments, the functionality described herein may be used in aheadset that combines images of an environment external to the near-eyedisplay 120 and artificial reality content (e.g., computer-generatedimages). Therefore, the near-eye display 120 may augment images of aphysical, real-world environment external to the near-eye display 120with generated content (e.g., images, video, sound, etc.) to present anaugmented reality to a user.

In various embodiments, the near-eye display 120 may include one or moreof display electronics 122, display optics 124, and an eye-tracking unit130. In some embodiments, the near-eye display 120 may also include oneor more locators 126, one or more position sensors 128, and an inertialmeasurement unit (IMU) 132. The near-eye display 120 may omit any of theeye-tracking unit 130, the locators 126, the position sensors 128, andthe IMU 132, or include additional elements in various embodiments.Additionally, in some embodiments, the near-eye display 120 may includeelements combining the function of various elements described inconjunction with FIG. 1.

The display electronics 122 may display or facilitate the display ofimages to the user according to data received from, for example, theconsole 110. In various embodiments, the display electronics 122 mayinclude one or more display panels, such as a liquid crystal display(LCD), an organic light emitting diode (OLED) display, an inorganiclight emitting diode (ILED) display, a micro light emitting diode(micro-LED) display, an active-matrix OLED display (AMOLED), atransparent OLED display (TOLED), or some other display. For example, inone implementation of the near-eye display 120, the display electronics122 may include a front TOLED panel, a rear display panel, and anoptical component (e.g., an attenuator, polarizer, or diffractive orspectral film) between the front and rear display panels. The displayelectronics 122 may include pixels to emit light of a predominant colorsuch as red, green, blue, white, or yellow. In some implementations, thedisplay electronics 122 may display a three-dimensional (3D) imagethrough stereoscopic effects produced by two-dimensional (2D) panels tocreate a subjective perception of image depth. For example, the displayelectronics 122 may include a left display and a right displaypositioned in front of a user's left eye and right eye, respectively.The left and right displays may present copies of an image shiftedhorizontally relative to each other to create a stereoscopic effect(i.e., a perception of image depth by a user viewing the image).

In certain embodiments, the display optics 124 may display image contentoptically (e.g., using optical waveguides and couplers) or magnify imagelight received from the display electronics 122, correct optical errorsassociated with the image light, and present the corrected image lightto a user of the near-eye display 120. In various embodiments, thedisplay optics 124 may include one or more optical elements, such as,for example, a substrate, optical waveguides, an aperture, a Fresnellens, a convex lens, a concave lens, a filter, input/output couplers, orany other suitable optical elements that may affect image light emittedfrom the display electronics 122. The display optics 124 may include acombination of different optical elements as well as mechanicalcouplings to maintain relative spacing and orientation of the opticalelements in the combination. One or more optical elements in the displayoptics 124 may have an optical coating, such as an anti-reflectivecoating, a reflective coating, a filtering coating, or a combination ofdifferent optical coatings.

Magnification of the image light by the display optics 124 may allow thedisplay electronics 122 to be physically smaller, weigh less, andconsume less power than larger displays. Additionally, magnification mayincrease a field of view of the displayed content. The amount ofmagnification of image light by the display optics 124 may be changed byadjusting, adding, or removing optical elements from the display optics124. In some embodiments, the display optics 124 may project displayedimages to one or more image planes that may be further away from theuser's eyes than the near-eye display 120.

The display optics 124 may also be designed to correct one or more typesof optical errors, such as 2D optical errors, 3D optical errors, or anycombination thereof. Two-dimensional errors may include opticalaberrations that occur in two dimensions. Example types of 2D errors mayinclude barrel distortion, pincushion distortion, longitudinal chromaticaberration, and transverse chromatic aberration. Three-dimensionalerrors may include optical errors that occur in three dimensions.Example types of 3D errors may include spherical aberration, comaticaberration, field curvature, and astigmatism.

The locators 126 may be objects located in specific positions on thenear-eye display 120 relative to one another and relative to a referencepoint on the near-eye display 120. In some implementations, the console110 may identify the locators 126 in images captured by the externalimaging device 150 to determine the artificial reality headset'sposition, orientation, or both. A locator 126 may be an LED, a cornercube reflector, a reflective marker, a type of light source thatcontrasts with an environment in which the near-eye display 120operates, or any combination thereof. In embodiments where the locators126 are active components (e.g., LEDs or other types of light emittingdevices), the locators 126 may emit light in the visible band (e.g.,about 380 nm to 750 nm), in the infrared (IR) band (e.g., about 750 nmto 1 mm), in the ultraviolet band (e.g., about 10 nm to about 380 nm),in another portion of the electromagnetic spectrum, or in anycombination of portions of the electromagnetic spectrum.

The external imaging device 150 may include one or more cameras, one ormore video cameras, any other device capable of capturing imagesincluding one or more of the locators 126, or any combination thereof.Additionally, the external imaging device 150 may include one or morefilters (e.g., to increase signal to noise ratio). The external imagingdevice 150 may be configured to detect light emitted or reflected fromthe locators 126 in a field of view of the external imaging device 150.In embodiments where the locators 126 include passive elements (e.g.,retroreflectors), the external imaging device 150 may include a lightsource that illuminates some or all of the locators 126, which mayretro-reflect the light to the light source in the external imagingdevice 150. Slow calibration data may be communicated from the externalimaging device 150 to the console 110, and the external imaging device150 may receive one or more calibration parameters from the console 110to adjust one or more imaging parameters (e.g., focal length, focus,frame rate, sensor temperature, shutter speed, aperture, etc.).

The position sensors 128 may generate one or more measurement signals inresponse to motion of the near-eye display 120. Examples of positionsensors 128 may include accelerometers, gyroscopes, magnetometers, othermotion-detecting or error-correcting sensors, or any combinationthereof. For example, in some embodiments, the position sensors 128 mayinclude multiple accelerometers to measure translational motion (e.g.,forward/back, up/down, or left/right) and multiple gyroscopes to measurerotational motion (e.g., pitch, yaw, or roll). In some embodiments,various position sensors may be oriented orthogonally to each other.

The IMU 132 may be an electronic device that generates fast calibrationdata based on measurement signals received from one or more of theposition sensors 128. The position sensors 128 may be located externalto the IMU 132, internal to the IMU 132, or any combination thereof.Based on the one or more measurement signals from one or more positionsensors 128, the IMU 132 may generate fast calibration data indicatingan estimated position of the near-eye display 120 relative to an initialposition of the near-eye display 120. For example, the IMU 132 mayintegrate measurement signals received from accelerometers over time toestimate a velocity vector and integrate the velocity vector over timeto determine an estimated position of a reference point on the near-eyedisplay 120. Alternatively, the IMU 132 may provide the sampledmeasurement signals to the console 110, which may determine the fastcalibration data. While the reference point may generally be defined asa point in space, in various embodiments, the reference point may alsobe defined as a point within the near-eye display 120 (e.g., a center ofthe IMU 132).

The eye-tracking unit 130 may include one or more eye-tracking systems.Eye tracking may refer to determining an eye's position, includingorientation and location of the eye, relative to the near-eye display120. An eye-tracking system may include an imaging system to image oneor more eyes and may optionally include a light emitter, which maygenerate light that is directed to an eye such that light reflected bythe eye may be captured by the imaging system. For example, theeye-tracking unit 130 may include a non-coherent or coherent lightsource (e.g., a laser diode) emitting light in the visible spectrum orinfrared spectrum, and a camera capturing the light reflected by theuser's eye. As another example, the eye-tracking unit 130 may capturereflected radio waves emitted by a miniature radar unit. Theeye-tracking unit 130 may use low-power light emitters that emit lightat frequencies and intensities that would not injure the eye or causephysical discomfort. The eye-tracking unit 130 may be arranged toincrease contrast in images of an eye captured by the eye-tracking unit130 while reducing the overall power consumed by the eye-tracking unit130 (e.g., reducing power consumed by a light emitter and an imagingsystem included in the eye-tracking unit 130). For example, in someimplementations, the eye-tracking unit 130 may consume less than 100milliwatts of power.

The near-eye display 120 may use the orientation of the eye to, e.g.,determine an inter-pupillary distance (IPD) of the user, determine gazedirection, introduce depth cues (e.g., blur image outside of the user'smain line of sight), collect heuristics on the user interaction in theVR media (e.g., time spent on any particular subject, object, or frameas a function of exposed stimuli), some other functions that are basedin part on the orientation of at least one of the user's eyes, or anycombination thereof. Because the orientation may be determined for botheyes of the user, the eye-tracking unit 130 may be able to determinewhere the user is looking. For example, determining a direction of auser's gaze may include determining a point of convergence based on thedetermined orientations of the user's left and right eyes. A point ofconvergence may be the point where the two foveal axes of the user'seyes intersect. The direction of the user's gaze may be the direction ofa line passing through the point of convergence and the mid-pointbetween the pupils of the user's eyes.

The input/output interface 140 may be a device that allows a user tosend action requests to the console 110. An action request may be arequest to perform a particular action. For example, an action requestmay be to start or to end an application or to perform a particularaction within the application. The input/output interface 140 mayinclude one or more input devices. Example input devices may include akeyboard, a mouse, a game controller, a glove, a button, a touch screen,or any other suitable device for receiving action requests andcommunicating the received action requests to the console 110. An actionrequest received by the input/output interface 140 may be communicatedto the console 110, which may perform an action corresponding to therequested action. In some embodiments, the input/output interface 140may provide haptic feedback to the user in accordance with instructionsreceived from the console 110. For example, the input/output interface140 may provide haptic feedback when an action request is received, orwhen the console 110 has performed a requested action and communicatesinstructions to the input/output interface 140. In some embodiments, theexternal imaging device 150 may be used to track the input/outputinterface 140, such as tracking the location or position of a controller(which may include, for example, an IR light source) or a hand of theuser to determine the motion of the user. In some embodiments, thenear-eye display 120 may include one or more imaging devices to trackthe input/output interface 140, such as tracking the location orposition of a controller or a hand of the user to determine the motionof the user.

The console 110 may provide content to the near-eye display 120 forpresentation to the user in accordance with information received fromone or more of the external imaging device 150, the near-eye display120, and the input/output interface 140. In the example shown in FIG. 1,the console 110 may include an application store 112, a headset trackingmodule 114, an artificial reality engine 116, and an eye-tracking module118. Some embodiments of the console 110 may include different oradditional modules than those described in conjunction with FIG. 1.Functions further described below may be distributed among components ofthe console 110 in a different manner than is described here.

In some embodiments, the console 110 may include a processor and anon-transitory computer-readable storage medium storing instructionsexecutable by the processor. The processor may include multipleprocessing units executing instructions in parallel. The non-transitorycomputer-readable storage medium may be any memory, such as a hard diskdrive, a removable memory, or a solid-state drive (e.g., flash memory ordynamic random access memory (DRAM)). In various embodiments, themodules of the console 110 described in conjunction with FIG. 1 may beencoded as instructions in the non-transitory computer-readable storagemedium that, when executed by the processor, cause the processor toperform the functions further described below.

The application store 112 may store one or more applications forexecution by the console 110. An application may include a group ofinstructions that, when executed by a processor, generates content forpresentation to the user. Content generated by an application may be inresponse to inputs received from the user via movement of the user'seyes or inputs received from the input/output interface 140. Examples ofthe applications may include gaming applications, conferencingapplications, video playback application, or other suitableapplications.

The headset tracking module 114 may track movements of the near-eyedisplay 120 using slow calibration information from the external imagingdevice 150. For example, the headset tracking module 114 may determinepositions of a reference point of the near-eye display 120 usingobserved locators from the slow calibration information and a model ofthe near-eye display 120. The headset tracking module 114 may alsodetermine positions of a reference point of the near-eye display 120using position information from the fast calibration information.Additionally, in some embodiments, the headset tracking module 114 mayuse portions of the fast calibration information, the slow calibrationinformation, or any combination thereof, to predict a future location ofthe near-eye display 120. The headset tracking module 114 may providethe estimated or predicted future position of the near-eye display 120to the artificial reality engine 116.

The artificial reality engine 116 may execute applications within theartificial reality system environment 100 and receive positioninformation of the near-eye display 120, acceleration information of thenear-eye display 120, velocity information of the near-eye display 120,predicted future positions of the near-eye display 120, or anycombination thereof from the headset tracking module 114. The artificialreality engine 116 may also receive estimated eye position andorientation information from the eye-tracking module 118. Based on thereceived information, the artificial reality engine 116 may determinecontent to provide to the near-eye display 120 for presentation to theuser. For example, if the received information indicates that the userhas looked to the left, the artificial reality engine 116 may generatecontent for the near-eye display 120 that mirrors the user's eyemovement in a virtual environment. Additionally, the artificial realityengine 116 may perform an action within an application executing on theconsole 110 in response to an action request received from theinput/output interface 140, and provide feedback to the user indicatingthat the action has been performed. The feedback may be visual oraudible feedback via the near-eye display 120 or haptic feedback via theinput/output interface 140.

The eye-tracking module 118 may receive eye-tracking data from theeye-tracking unit 130 and determine the position of the user's eye basedon the eye tracking data. The position of the eye may include an eye'sorientation, location, or both relative to the near-eye display 120 orany element thereof. Because the eye's axes of rotation change as afunction of the eye's location in its socket, determining the eye'slocation in its socket may allow the eye-tracking module 118 to moreaccurately determine the eye's orientation.

FIG. 2 is a perspective view of a near-eye display in the form of ahead-mounted display (HMD) device 200, in accordance with one or moreembodiments. The HMD device 200 may be a part of, e.g., a VR system, anAR system, an MR system, or any combination thereof. The HMD device 200may include a body 220 and a head strap 230. FIG. 2 shows a bottom side223, a front side 225, and a left side 227 of the body 220 in theperspective view. The head strap 230 may have an adjustable orextendible length. There may be a sufficient space between the body 220and the head strap 230 of the HMD device 200 for allowing a user tomount the HMD device 200 onto the user's head. In various embodiments,the HMD device 200 may include additional, fewer, or differentcomponents. For example, in some embodiments, the HMD device 200 mayinclude eyeglass temples and temple tips as shown in, for example, FIG.3 below, rather than the head strap 230.

The HMD device 200 may present to a user media including virtual and/oraugmented views of a physical, real-world environment withcomputer-generated elements. Examples of the media presented by the HMDdevice 200 may include images (e.g., 2D or 3D images), videos (e.g., 2Dor 3D videos), audio, or any combination thereof. The images and videosmay be presented to each eye of the user by one or more displayassemblies (not shown in FIG. 2) enclosed in the body 220 of the HMDdevice 200. In various embodiments, the one or more display assembliesmay include a single electronic display panel or multiple electronicdisplay panels (e.g., one display panel for each eye of the user).Examples of the electronic display panel(s) may include, for example, anLCD, an OLED display, an ILED display, a micro-LED display, an AMOLED, aTOLED, some other display, or any combination thereof. The HMD device200 may include two eye box regions.

In some implementations, the HMD device 200 may include various sensors(not shown), such as depth sensors, motion sensors, position sensors,and eye tracking sensors. Some of these sensors may use a structuredlight pattern for sensing. In some implementations, the HMD device 200may include an input/output interface for communicating with a console.In some implementations, the HMD device 200 may include a virtualreality engine (not shown) that can execute applications within the HMDdevice 200 and receive depth information, position information,acceleration information, velocity information, predicted futurepositions, or any combination thereof of the HMD device 200 from thevarious sensors. In some implementations, the information received bythe virtual reality engine may be used for producing a signal (e.g.,display instructions) to the one or more display assemblies. In someimplementations, the HMD device 200 may include locators (not shown,such as the locators 126) located in fixed positions on the body 220relative to one another and relative to a reference point. Each of thelocators may emit light that is detectable by an external imagingdevice.

FIG. 3 is a perspective view of a near-eye display 300 in the form of apair of glasses, in accordance with one or more embodiments. Thenear-eye display 300 may be a specific implementation of the near-eyedisplay 120 of FIG. 1, and may be configured to operate as a VR display,an AR display, and/or a MR display. The near-eye display 300 may includea frame 305 and a display 310. The display 310 may be configured topresent content to a user. In some embodiments, the display 310 mayinclude display electronics and/or display optics. For example, asdescribed above with respect to the near-eye display 120 of FIG. 1, thedisplay 310 may include an LCD display panel, an LED display panel, oran optical display panel (e.g., a waveguide display assembly).

The near-eye display 300 may further include various sensors 350 a, 350b, 350 c, 350 d, and 350 e on or within the frame 305. In someembodiments, the sensors 350 a-350 e may include one or more depthsensors, motion sensors, position sensors, inertial sensors, or ambientlight sensors. In some embodiments, the sensors 350 a-350 e may includeone or more image sensors configured to generate image data representingdifferent fields of views in different directions. In some embodiments,the sensors 350 a-350 e may be used as input devices to control orinfluence the displayed content of the near-eye display 300, and/or toprovide an interactive VR/AR/MR experience to a user of the near-eyedisplay 300. In some embodiments, the sensors 350 a-350 e may also beused for stereoscopic imaging.

In some embodiments, the near-eye display 300 may further include one ormore illuminators 330 to project light into the physical environment.The projected light may be associated with different frequency bands(e.g., visible light, infra-red light, ultra-violet light, etc.), andmay serve various purposes. For example, the illuminator(s) 330 mayproject light in a dark environment (or in an environment with lowintensity of infra-red light, ultra-violet light, etc.) to assist thesensors 350 a-350 e in capturing images of different objects within thedark environment. In some embodiments, the illuminator(s) 330 may beused to project certain light pattern onto the objects within theenvironment. In some embodiments, the illuminator(s) 330 may be used aslocators, such as the locators 126 described above with respect to FIG.1.

In some embodiments, the near-eye display 300 may also include ahigh-resolution camera 340. The camera 340 may capture images of thephysical environment in the field of view. The captured images may beprocessed, for example, by a virtual reality engine (e.g., theartificial reality engine 116 of FIG. 1) to add virtual objects to thecaptured images or modify physical objects in the captured images, andthe processed images may be displayed to the user by the display 310 forAR or MR applications.

FIG. 4 illustrates an optical see-through augmented reality system 400including a waveguide display, in accordance with one or moreembodiments. The augmented reality system 400 may include a projector410 and a combiner 415. The projector 410 may include a light source orimage source 412 and projector optics 414. In some embodiments, thelight source or image source 412 may include one or more micro-LEDdevices described above. In some embodiments, the image source 412 mayinclude a plurality of pixels that displays virtual objects, such as anLCD display panel or an LED display panel. In some embodiments, thelight source 412 may include a light source that generates coherent orpartially coherent light. For example, the light source 412 may includea laser diode, a vertical cavity surface emitting laser, an LED, and/ora micro-LED described above. In some embodiments, the light source 412may include a plurality of light sources (e.g., an array of micro-LEDsdescribed above) each emitting a monochromatic image light correspondingto a primary color (e.g., red, green, or blue). In some embodiments, thelight source 412 may include three 2D arrays of micro-LEDs, where each2D array of micro-LEDs may include micro-LEDs configured to emit lightof a primary color (e.g., red, green, or blue). In some embodiments, thelight source 412 may include an optical pattern generator, such as aspatial light modulator. The projector optics 414 may include one ormore optical components that can condition the light from the lightsource 412, such as expanding, collimating, scanning, or projectinglight from the light source 412 to the combiner 415. The one or moreoptical components may include, for example, one or more lenses, liquidlenses, mirrors, apertures, and/or gratings. For example, in someembodiments, the light source 412 may include one or moreone-dimensional arrays or elongated 2D arrays of micro-LEDs, and theprojector optics 414 may include one or more one-dimensional scanners(e.g., micro-mirrors or prisms) configured to scan the one-dimensionalarrays or elongated 2D arrays of micro-LEDs to generate image frames. Insome embodiments, the projector optics 414 may include a liquid lens(e.g., a liquid crystal lens) with a plurality of electrodes that allowsscanning of the light from the light source 412.

The combiner 415 may include an input coupler 430 for coupling lightfrom the projector 410 into a substrate 420 of the combiner 415. Thecombiner 415 may transmit at least 50% of light in a first wavelengthrange and reflect at least 25% of light in a second wavelength range.For example, the first wavelength range may be visible light from about400 nm to about 650 nm, and the second wavelength range may be in theinfrared band, for example, from about 800 nm to about 1000 nm. Theinput coupler 430 may include a volume holographic grating, adiffractive optical element (DOE) (e.g., a surface-relief grating), aslanted surface of the substrate 420, or a refractive coupler (e.g., awedge or a prism). The input coupler 430 may have a coupling efficiencyof greater than 30%, 50%, 75%, 90%, or higher for visible light. Lightcoupled into the substrate 420 may propagate within the substrate 420through, for example, total internal reflection (TIR). The substrate 420may be in the form of a lens of a pair of eyeglasses. The substrate 420may have a flat or a curved surface, and may include one or more typesof dielectric materials, such as glass, quartz, plastic, polymer,poly(methyl methacrylate) (PMMA), crystal, or ceramic. A thickness ofthe substrate 420 may range from, for example, less than about 1 mm toabout 10 mm or more. The substrate 420 may be transparent to visiblelight.

The substrate 420 may include or may be coupled to a plurality of outputcouplers 440 configured to extract at least a portion of the lightguided by and propagating within the substrate 420 from the substrate420, and direct extracted light 460 to an eye 490 of the user of theaugmented reality system 400. As the input coupler 430, the outputcouplers 440 may include grating couplers (e.g., volume holographicgratings or surface-relief gratings), other DOEs, prisms, etc. Theoutput couplers 440 may have different coupling (e.g., diffraction)efficiencies at different locations. The substrate 420 may also allowlight 450 from the environment in front of the combiner 415 to passthrough with little or no loss. The output couplers 440 may also allowthe light 450 to pass through with little loss. For example, in someimplementations, the output couplers 440 may have a low diffractionefficiency for the light 450 such that the light 450 may be refracted orotherwise pass through the output couplers 440 with little loss, andthus may have a higher intensity than the extracted light 460. In someimplementations, the output couplers 440 may have a high diffractionefficiency for the light 450 and may diffract the light 450 to certaindesired directions (i.e., diffraction angles) with little loss. As aresult, the user may be able to view combined images of the environmentin front of the combiner 415 and virtual objects projected by theprojector 410.

FIG. 5A illustrates an example of a near-eye display device 500including a waveguide display 530, in accordance with one or moreembodiments. The near-eye display device 500 may be an example of thenear-eye display 120, the augmented reality system 400, or another typeof display device. The near-eye display device 500 may include a lightsource 510, projection optics 520, and a waveguide display 530. Thelight source 510 may include multiple panels of light emitters fordifferent colors, such as a panel of red light emitters 512, a panel ofgreen light emitters 514, and a panel of blue light emitters 516. Thered light emitters 512 are organized into an array; the green lightemitters 514 are organized into an array; and the blue light emitters516 are organized into an array. The dimensions and pitches of the lightemitters in the light source 510 may be small. For example, each lightemitter may have a diameter less than 2 μm (e.g., about 1.2 pm) and thepitch may be less than 2 μm (e.g., about 1.5 μm). As such, the number oflight emitters in each of the red light emitters 512, the green lightemitters 514, and the blue light emitters 516 can be equal to or greaterthan the number of pixels in a display image, such as 960×720, 1280×720,1440×1080, 1920×1080, 2160×1080, or 2560×1080 pixels. Thus, a displayimage may be generated simultaneously by the light source 510. Ascanning element may not be used in the near-eye display device 500.

Before reaching the waveguide display 530, the light emitted by thelight source 510 may be conditioned by the projection optics 520, whichmay include a lens array. The projection optics 520 may collimate orfocus the light emitted by the light source 510 to the waveguide display530, which may include a coupler 532 for coupling the light emitted bythe light source 510 into the waveguide display 530. The light coupledinto the waveguide display 530 may propagate within the waveguidedisplay 530 through, for example, total internal reflection as describedabove with respect to FIG. 4. The coupler 532 may also couple portionsof the light propagating within the waveguide display 530 out of thewaveguide display 530 and towards a user's eye 590.

FIG. 5B illustrates an example of a near-eye display device 550including a waveguide display 580, in accordance with one or moreembodiments. In some embodiments, the near-eye display device 550 mayuse a scanning mirror 570 to project light from a light source 540 to animage field where a user's eye 590 may be located. The near-eye displaydevice 550 may be an example of the near-eye display 120, the augmentedreality system 400, or another type of display device. A light source540 may include one or more rows or one or more columns of lightemitters of different colors, such as multiple rows of red lightemitters 542, multiple rows of green light emitters 544, and multiplerows of blue light emitters 546. For example, the red light emitters542, the green light emitters 544, and the blue light emitters 546 mayeach include N rows, each row including, for example, 2,560 lightemitters (pixels). The red light emitters 542 are organized into anarray; the green light emitters 544 are organized into an array; and theblue light emitters 546 are organized into an array. In someembodiments, the light source 540 may include a single line of lightemitters for each color. In some embodiments, the light source 540 mayinclude multiple columns of light emitters for each of red, green, andblue colors, where each column may include, for example, 1,080 lightemitters. In some embodiments, the dimensions and/or pitches of thelight emitters in the light source 540 may be relatively large (e.g.,about 3-5 μm) and thus the light source 540 may not include sufficientlight emitters for simultaneously generating a full display image. Forexample, the number of light emitters for a single color may be fewerthan the number of pixels (e.g., 2560×1080 pixels) in a display image.The light emitted by the light source 540 may be a set of collimated ordiverging beams of light.

Before reaching the scanning mirror 570, the light emitted by the lightsource 540 may be conditioned by various optical devices, such ascollimating lenses or a freeform optical element 560. The freeformoptical element 560 may include, for example, a multi-facets prism oranother light folding element that may direct the light emitted by thelight source 540 towards the scanning mirror 570, such as changing thepropagation direction of the light emitted by the light source 540 by,for example, about 90° or larger. In some embodiments, the freeformoptical element 560 may be rotatable to scan the light. The scanningmirror 570 and/or the freeform optical element 560 may reflect andproject the light emitted by the light source 540 to the waveguidedisplay 580, which may include a coupler 582 for coupling the lightemitted by the light source 540 into the waveguide display 580. Thelight coupled into the waveguide display 580 may propagate within thewaveguide display 580 through, for example, total internal reflection asdescribed above with respect to FIG. 4. The coupler 582 may also coupleportions of the light propagating within the waveguide display 580 outof the waveguide display 580 and towards the user's eye 590.

The scanning mirror 570 may include a microelectromechanical system(MEMS) mirror or any other suitable mirrors. The scanning mirror 570 mayrotate to scan in one or two dimensions. As the scanning mirror 570rotates, the light emitted by the light source 540 may be directed todifferent areas of the waveguide display 580 such that a full displayimage may be projected onto the waveguide display 580 and directed tothe user's eye 590 by the waveguide display 580 in each scanning cycle.For example, in embodiments where the light source 540 includes lightemitters for all pixels in one or more rows or columns, the scanningmirror 570 may be rotated in the column or row direction (e.g., x or ydirection) to scan an image. In embodiments where the light source 540includes light emitters for some but not all pixels in one or more rowsor columns, the scanning mirror 570 may be rotated in both the row andcolumn directions (e.g., both x and y directions) to project a displayimage (e.g., using a raster-type scanning pattern).

The near-eye display device 550 may operate in predefined displayperiods. A display period (e.g., display cycle) may refer to a durationof time in which a full image is scanned or projected. For example, adisplay period may be a reciprocal of the desired frame rate. In thenear-eye display device 550 that includes the scanning mirror 570, thedisplay period may also be referred to as a scanning period or scanningcycle. The light generation by the light source 540 may be synchronizedwith the rotation of the scanning mirror 570. For example, each scanningcycle may include multiple scanning steps, where the light source 540may generate a different light pattern in each respective scanning step.

In each scanning cycle, as the scanning mirror 570 rotates, a displayimage may be projected onto the waveguide display 580 and the user's eye590. The actual color value and light intensity (e.g., brightness) of agiven pixel location of the display image may be an average of the lightbeams of the three colors (e.g., red, green, and blue) illuminating thepixel location during the scanning period. After completing a scanningperiod, the scanning mirror 570 may revert back to the initial positionto project light for the first few rows of the next display image or mayrotate in a reverse direction or scan pattern to project light for thenext display image, where a new set of driving signals may be fed to thelight source 540. The same process may be repeated as the scanningmirror 570 rotates in each scanning cycle. As such, different images maybe projected to the user's eye 590 in different scanning cycles.

FIG. 6 illustrates an image source assembly 610 in a near-eye displaysystem 600, in accordance with one or more embodiments. The image sourceassembly 610 may include, for example, a display panel 640 that maygenerate display images to be projected to the user's eyes, and aprojector 650 that may project the display images generated by thedisplay panel 640 to a waveguide display as described above with respectto FIGS. 4-5B. The display panel 640 may include a light source 642 anda driver circuit 644 for the light source 642. The light source 642 mayinclude, for example, the light source 510 or 540. The projector 650 mayinclude, for example, the freeform optical element 560, the scanningmirror 570, and/or the projection optics 520 described above in FIGS.5A-5B. The near-eye display system 600 may also include a controller 620that synchronously controls the light source 642 and the projector 650(e.g., the scanning mirror 570). The image source assembly 610 maygenerate and output an image light to a waveguide display (not shown inFIG. 6), such as the waveguide display 530 or 580. As described above,the waveguide display may receive the image light at one or moreinput-coupling elements, and guide the received image light to one ormore output-coupling elements. The input and output coupling elementsmay include, for example, a diffraction grating, a holographic grating,a prism, or any combination thereof. The input-coupling element may bechosen such that total internal reflection occurs with the waveguidedisplay. The output-coupling element may couple portions of the totalinternally reflected image light out of the waveguide display.

As described above, the light source 642 may include a plurality oflight emitters arranged in an array or a matrix. Each light emitter mayemit monochromatic light, such as red light, blue light, green light,infra-red light, and the like. While RGB colors are often discussed inthis disclosure, embodiments described herein are not limited to usingred, green, and blue as primary colors. Other colors can also be used asthe primary colors of the near-eye display system 600. In someembodiments, a display panel in accordance with an embodiment may usemore than three primary colors. Each pixel in the light source 642 mayinclude three subpixels that include a red micro-LED, a green micro-LED,and a blue micro-LED. A semiconductor LED generally includes an activelight emitting layer within multiple layers of semiconductor materials.The multiple layers of semiconductor materials may include differentcompound materials or a same base material with different dopants and/ordifferent doping densities. For example, the multiple layers ofsemiconductor materials may include an n-type material layer, an activeregion that may include hetero-structures (e.g., one or more quantumwells), and a p-type material layer. The multiple layers ofsemiconductor materials may be grown on a surface of a substrate havinga certain orientation. In some embodiments, to increase light extractionefficiency, a mesa that includes at least some of the layers ofsemiconductor materials may be formed.

The controller 620 may control the image rendering operations of theimage source assembly 610, such as the operations of the light source642 and/or the projector 650. For example, the controller 620 maydetermine instructions for the image source assembly 610 to render oneor more display images. The instructions may include displayinstructions and scanning instructions. In some embodiments, the displayinstructions may include an image file (e.g., a bitmap file). Thedisplay instructions may be received from, for example, a console, suchas the console 110 described above with respect to FIG. 1. The scanninginstructions may be used by the image source assembly 610 to generateimage light. The scanning instructions may specify, for example, a typeof a source of image light (e.g., monochromatic or polychromatic), ascanning rate, an orientation of a scanning apparatus, one or moreillumination parameters, or any combination thereof. The controller 620may include a combination of hardware, software, and/or firmware notshown here so as not to obscure other aspects of the present disclosure.

In some embodiments, the controller 620 may be a graphics processingunit (GPU) of a display device. In other embodiments, the controller 620may be other kinds of processors. The operations performed by thecontroller 620 may include taking content for display and dividing thecontent into discrete sections. The controller 620 may provide to thelight source 642 scanning instructions that include an addresscorresponding to an individual source element of the light source 642and/or an electrical bias applied to the individual source element. Thecontroller 620 may instruct the light source 642 to sequentially presentthe discrete sections using light emitters corresponding to one or morerows of pixels in an image ultimately displayed to the user. Thecontroller 620 may also instruct the projector 650 to perform differentadjustments of the light. For example, the controller 620 may controlthe projector 650 to scan the discrete sections to different areas of acoupling element of the waveguide display (e.g., the waveguide display580) as described above with respect to FIG. 5B. As such, at the exitpupil of the waveguide display, each discrete portion is presented in adifferent respective location. While each discrete section is presentedat a different respective time, the presentation and scanning of thediscrete sections occur fast enough such that a user's eye may integratethe different sections into a single image or series of images.

An image processor 630 may be a general-purpose processor and/or one ormore application-specific circuits that are dedicated to performing thefeatures described herein. In one embodiment, a general-purposeprocessor may be coupled to a memory to execute software instructionsthat cause the processor to perform certain processes described herein.In another embodiment, the image processor 630 may be one or morecircuits that are dedicated to performing certain features. While theimage processor 630 in FIG. 6 is shown as a stand-alone unit that isseparate from the controller 620 and the driver circuit 644, the imageprocessor 630 may be a sub-unit of the controller 620 or the drivercircuit 644 in other embodiments. In other words, in those embodiments,the controller 620 or the driver circuit 644 may perform various imageprocessing functions of the image processor 630. The image processor 630may also be referred to as an image processing circuit.

In the example shown in FIG. 6, the light source 642 may be driven bythe driver circuit 644, based on data or instructions (e.g., display andscanning instructions) sent from the controller 620 or the imageprocessor 630. In one embodiment, the driver circuit 644 may include acircuit panel that connects to and mechanically holds various lightemitters of the light source 642. The light source 642 may emit light inaccordance with one or more illumination parameters that are set by thecontroller 620 and potentially adjusted by the image processor 630 andthe driver circuit 644. An illumination parameter may be used by thelight source 642 to generate light. An illumination parameter mayinclude, for example, source wavelength, pulse rate, pulse amplitude,beam type (continuous or pulsed), other parameter(s) that may affect theemitted light, or any combination thereof. In some embodiments, thesource light generated by the light source 642 may include multiplebeams of red light, green light, and blue light, or any combinationthereof.

The projector 650 may perform a set of optical functions, such asfocusing, combining, conditioning, or scanning the image light generatedby the light source 642. In some embodiments, the projector 650 mayinclude a combining assembly, a light conditioning assembly, or ascanning mirror assembly. The projector 650 may include one or moreoptical components that optically adjust and potentially re-direct thelight from the light source 642. One example of the adjustment of lightmay include conditioning the light, such as expanding, collimating,correcting for one or more optical errors (e.g., field curvature,chromatic aberration, etc.), some other adjustments of the light, or anycombination thereof. The optical components of the projector 650 mayinclude, for example, lenses, mirrors, apertures, gratings, or anycombination thereof.

The projector 650 may redirect image light via its one or morereflective and/or refractive portions so that the image light isprojected at certain orientations toward the waveguide display. Thelocation where the image light is redirected toward may depend onspecific orientations of the one or more reflective and/or refractiveportions. In some embodiments, the projector 650 includes a singlescanning mirror that scans in at least two dimensions. In otherembodiments, the projector 650 may include a plurality of scanningmirrors that each scan in directions orthogonal to each other. Theprojector 650 may perform a raster scan (horizontally or vertically), abi-resonant scan, or any combination thereof. In some embodiments, theprojector 650 may perform a controlled vibration along the horizontaland/or vertical directions with a specific frequency of oscillation toscan along two dimensions and generate a 2D projected image of the mediapresented to user's eyes. In other embodiments, the projector 650 mayinclude a lens or prism that may serve similar or the same function asone or more scanning mirrors. In some embodiments, the image sourceassembly 610 may not include a projector, where the light emitted by thelight source 642 may be directly incident on the waveguide display.

FIG. 7A illustrates a light emitting diode (LED) 700 having a verticalmesa structure, in accordance with one or more embodiments. The LED 700may be a light emitter in the light source 510, 540, or 642. The LED 700may be a micro-LED made of inorganic materials, such as multiple layersof semiconductor materials. The layered semiconductor light emittingdevice may include multiple layers of III-V semiconductor materials. AIII-V semiconductor material may include one or more Group III elements,such as aluminum (Al), gallium (Ga), or indium (In), in combination witha Group V element, such as nitrogen (N), phosphorus (P), arsenic (As),or antimony (Sb). When the Group V element of the III-V semiconductormaterial includes nitrogen, the III-V semiconductor material is referredto as a III-nitride material. The layered semiconductor light emittingdevice may be manufactured by growing multiple epitaxial layers on asubstrate using techniques such as vapor-phase epitaxy (VPE),liquid-phase epitaxy (LPE), molecular beam epitaxy (MBE), ormetalorganic chemical vapor deposition (MOCVD). For example, the layersof the semiconductor materials may be grown layer-by-layer on asubstrate with a certain crystal lattice orientation (e.g., polar,nonpolar, or semi-polar orientation), such as a GaN, GaAs, or GaPsubstrate, or a substrate including, but not limited to, sapphire,silicon carbide, silicon, zinc oxide, boron nitride, lithium aluminate,lithium niobate, germanium, aluminum nitride, lithium gallate, partiallysubstituted spinels, or quaternary tetragonal oxides sharing thebeta-LiAlO₂ structure, where the substrate may be cut in a specificdirection to expose a specific plane as the growth surface.

In the example shown in FIG. 7A, the LED 700 may include a substrate710, which may include, for example, a sapphire substrate or a GaNsubstrate. A semiconductor layer 720 may be grown on the substrate 710.The semiconductor layer 720 may include a III-V material, such as GaN,and may be p-doped (e.g., with Mg, Ca, Zn, or Be) or n-doped (e.g., withSi or Ge). One or more active layers 730 may be grown on thesemiconductor layer 720 to form an active region. The active layer 730may include III-V materials, such as one or more InGaN layers, one ormore AlInGaP layers, and/or one or more GaN layers, which may form oneor more heterostructures, such as one or more quantum wells or MQWs. Asemiconductor layer 740 may be grown on the active layer 730. Thesemiconductor layer 740 may include a III-V material, such as GaN, andmay be p-doped (e.g., with Mg, Ca, Zn, or Be) or n-doped (e.g., with Sior Ge). One of semiconductor layer 720 and semiconductor layer 740 maybe a p-type layer and the other one may be an n-type layer. Thesemiconductor layer 720 and the semiconductor layer 740 sandwich theactive layer 730 to form the light emitting region. For example, the LED700 may include a layer of InGaN situated between a layer of p-type GaNdoped with magnesium and a layer of n-type GaN doped with silicon oroxygen. In some embodiments, the LED 700 may include a layer of AlInGaPsituated between a layer of p-type AlInGaP doped with zinc or magnesiumand a layer of n-type AlInGaP doped with selenium, silicon, ortellurium.

In some embodiments, an electron-blocking layer (EBL) (not shown in FIG.7A) may be grown to form a layer between the active layer 730 and atleast one of the semiconductor layer 720 or the semiconductor layer 740.The EBL may reduce the electron leakage current and improve theefficiency of the LED. In some embodiments, a heavily-dopedsemiconductor layer 750, such as a P+ or P++ semiconductor layer, may beformed on the semiconductor layer 740 and act as a contact layer forforming an ohmic contact and reducing the contact impedance of thedevice. In some embodiments, a conductive layer 760 may be formed on theheavily-doped semiconductor layer 750. The conductive layer 760 mayinclude, for example, an indium tin oxide (ITO) or Al/Ni/Au film. In oneexample, the conductive layer 760 may include a transparent ITO layer.

To make contact with the semiconductor layer 720 (e.g., an n-GaN layer)and to more efficiently extract light emitted by the active layer 730from the LED 700, the semiconductor material layers (including theheavily-doped semiconductor layer 750, the semiconductor layer 740, theactive layer 730, and the semiconductor layer 720) may be etched toexpose the semiconductor layer 720 and to form a mesa structure thatincludes the layers 720-760. The mesa structure may confine the carrierswithin the device. Etching the mesa structure may lead to the formationof mesa sidewalls 732 that may be orthogonal to the growth planes. Apassivation layer 770 may be formed on the sidewalls 732 of the mesastructure. The passivation layer 770 may include an oxide layer, such asa SiO₂ layer, and may act as a reflector to reflect emitted light out ofthe LED 700. A contact layer 780, which may include a metal layer, suchas Al, Au, Ni, Ti, or any combination thereof, may be formed on thesemiconductor layer 720 and may act as an electrode of the LED 700. Inaddition, another contact layer 790, such as an Al/Ni/Au metal layer,may be formed on the conductive layer 760 and may act as anotherelectrode of the LED 700.

When a voltage signal is applied to the contact layers 780 and 790,electrons and holes may recombine in the active layer 730, where therecombination of electrons and holes may cause photon emission. Thewavelength and energy of the emitted photons may depend on the energybandgap between the valence band and the conduction band in the activelayer 730. For example, InGaN active layers may emit green or bluelight, AlGaN active layers may emit blue to ultraviolet light, whileAlInGaP active layers may emit red, orange, yellow, or green light. Theemitted photons may be reflected by the passivation layer 770 and mayexit the LED 700 from the top (e.g., the conductive layer 760 and thecontact layer 790) or bottom (e.g., the substrate 710).

In some embodiments, the LED 700 may include one or more othercomponents, such as a lens, on the light emission surface, such as thesubstrate 710, to focus or collimate the emitted light or couple theemitted light into a waveguide. In some embodiments, an LED may includea mesa of another shape, such as planar, conical, semi-parabolic, orparabolic, and a base area of the mesa may be circular, rectangular,hexagonal, or triangular. For example, the LED may include a mesa of acurved shape (e.g., paraboloid shape) and/or a non-curved shape (e.g.,conic shape). The mesa may be truncated or non-truncated.

FIG. 7B is a cross-sectional view of a LED 705 having a parabolic mesastructure, in accordance with one or more embodiments. Similar to theLED 700, LED 705 may include multiple layers of semiconductor materials,such as multiple layers of III-V semiconductor materials. Thesemiconductor material layers may be epitaxially grown on a substrate715, such as a GaN substrate or a sapphire substrate. For example, asemiconductor layer 725 may be grown on the substrate 715. Thesemiconductor layer 725 may include a III-V material, such as GaN, andmay be p-doped (e.g., with Mg, Ca, Zn, or Be) or n-doped (e.g., with Sior Ge). One or more active layers 735 may be grown on the semiconductorlayer 725. The active layer 735 may include III-V materials, such as oneor more InGaN layers, one or more AlInGaP layers, and/or one or more GaNlayers, which may form one or more heterostructures, such as one or morequantum wells. A semiconductor layer 745 may be grown on the activelayer 735. The semiconductor layer 745 may include a III-V material,such as GaN, and may be p-doped (e.g., with Mg, Ca, Zn, or Be) orn-doped (e.g., with Si or Ge). One of the semiconductor layer 725 andthe semiconductor layer 745 may be a p-type layer and the other one maybe an n-type layer.

To make contact with the semiconductor layer 725 (e.g., an n-type GaNlayer) and to more efficiently extract light emitted by the active layer735 from the LED 705, the semiconductor layers may be etched to exposethe semiconductor layer 725 and to form a mesa structure that includesthe layers 725-745. The mesa structure may confine carriers within theinjection area of the device. Etching the mesa structure may lead to theformation of mesa side walls (also referred to herein as facets) thatmay be non-parallel with, or in some cases, orthogonal, to the growthplanes associated with crystalline growth of the layers 725-745.

As shown in FIG. 7B, the LED 705 may have a mesa structure that includesa flat top. A dielectric layer 775 (e.g., SiO₂ or SiN_(x)) may be formedon the facets of the mesa structure. In some embodiments, the dielectriclayer 775 may include multiple layers of dielectric materials. In someembodiments, a metal layer 795 may be formed on the dielectric layer775. The metal layer 795 may include one or more metal or metal alloymaterials, such as aluminum (Al), silver (Ag), gold (Au), platinum (Pt),titanium (Ti), copper (Cu), or any combination thereof. The dielectriclayer 775 and the metal layer 795 may form a mesa reflector that canreflect light emitted by the active layer 735 toward the substrate 715.In some embodiments, the mesa reflector may be parabolic-shaped to actas a parabolic reflector that may at least partially collimate theemitted light.

An electrical contact 765 and an electrical contact 785 may be formed onthe semiconductor layer 745 and the semiconductor layer 725,respectively, to act as electrodes. The electrical contact 765 and theelectrical contact 785 may each include a conductive material, such asAl, Au, Pt, Ag, Ni, Ti, Cu, or any combination thereof (e.g., Ag/Pt/Auor Al/Ni/Au), and may act as the electrodes of the LED 705. In theexample shown in FIG. 7B, the electrical contact 785 may be ann-contact, and the electrical contact 765 may be a p-contact. Theelectrical contact 765 and the semiconductor layer 745 (e.g., a p-typesemiconductor layer) may form a back reflector for reflecting lightemitted by the active layer 735 back toward the substrate 715. In someembodiments, the electrical contact 765 and the metal layer 795 includesame material(s) and can be formed using the same processes. In someembodiments, an additional conductive layer (not shown) may be includedas an intermediate conductive layer between the electrical contacts 765and 785 and the semiconductor layers.

When a voltage signal is applied across the electrical contacts 765 and785, electrons and holes may recombine in the active layer 735. Therecombination of electrons and holes may cause photon emission, thusproducing light. The wavelength and energy of the emitted photons maydepend on the energy bandgap between the valence band and the conductionband in the active layer 735. For example, InGaN active layers may emitgreen or blue light, while AlInGaP active layers may emit red, orange,yellow, or green light. The emitted photons may propagate in manydifferent directions, and may be reflected by the mesa reflector and/orthe back reflector and may exit the LED 705, for example, from thebottom side (e.g., the substrate 715) shown in FIG. 7B. One or moreother secondary optical components, such as a lens or a grating, may beformed on the light emission surface, such as the substrate 715, tofocus or collimate the emitted light and/or couple the emitted lightinto a waveguide.

One or 2D arrays of the LEDs described above may be manufactured on awafer to form light sources (e.g., the light source 642). Drivercircuits (e.g., the driver circuit 644) may be fabricated, for example,on a silicon wafer using CMOS processes. The LEDs and the drivercircuits on wafers may be diced and then bonded together, or may bebonded on the wafer level and then diced. Various bonding techniques canbe used for bonding the LEDs and the driver circuits, such as adhesivebonding, metal-to-metal bonding, metal oxide bonding, wafer-to-waferbonding, die-to-wafer bonding, hybrid bonding, and the like.

FIG. 8A illustrates a method of die-to-wafer bonding for arrays of LEDs,in accordance with one or more embodiments. In the example shown in FIG.8A, an LED array 801 may include a plurality of LEDs 807 on a carriersubstrate 805. The carrier substrate 805 may include various materials,such as GaAs, InP, GaN, AlN, sapphire, SiC, Si, or the like. The LEDs807 may be fabricated by, for example, growing various epitaxial layers,forming mesa structures, and forming electrical contacts or electrodes,before performing the bonding. The epitaxial layers may include variousmaterials, such as GaN, InGaN, (AlGaIn)P, (AlGaIn)AsP, (AlGaIn)AsN,(AlGaIn)Pas, (Eu:InGa)N, (AlGaIn)N, or the like, and may include ann-type layer, a p-type layer, and an active layer that includes one ormore heterostructures, such as one or more quantum wells or MQWs. Theelectrical contacts may include various conductive materials, such as ametal or a metal alloy.

A wafer 803 may include a base layer 809 having passive or activeintegrated circuits (e.g., driver circuits 811) fabricated thereon. Thebase layer 809 may include, for example, a silicon wafer. The drivercircuits 811 may be used to control the operations of the LEDs 807. Forexample, the driver circuit for each of the LEDs 807 may include a 2T1Cpixel structure that has two transistors and one capacitor. The wafer803 may also include a bonding layer 813. The bonding layer 813 mayinclude various materials, such as a metal, an oxide, a dielectric,CuSn, AuTi, and the like. In some embodiments, a patterned layer 815 maybe formed on a surface of the bonding layer 813, where the patternedlayer 815 may include a metallic grid made of a conductive material,such as Cu, Ag, Au, Al, or the like.

An LED array 801 may be bonded to the wafer 803 via the bonding layer813 or the patterned layer 815. For example, the patterned layer 815 mayinclude metal pads, bumps, and/or interconnects made of variousmaterials, such as CuSn, AuSn, or nanoporous metal, that may be used toalign the LEDs 807 of the LED array 801 with corresponding drivercircuits 811 on the wafer 803. In one example, the LED array 801 may bebrought toward the wafer 803 until the LEDs 807 come into contact withrespective metal pads, bumps, and/or interconnects corresponding to thedriver circuits 811. Some or all of the LEDs 807 may be aligned with thedriver circuits 811, and may then be bonded to the wafer 803 via thepatterned layer 815 by various bonding techniques, such asmetal-to-metal bonding. After the LEDs 807 have been bonded to the wafer803, the carrier substrate 805 may be removed from the LEDs 807.

FIG. 8B illustrates a method of wafer-to-wafer bonding for arrays ofLEDs, in accordance with one or more embodiments. As shown in FIG. 8B, afirst wafer 802 may include a substrate 804, a first semiconductor layer806, one or more active layers 808, and a second semiconductor layer810. The substrate 804 may include various materials, such as GaAs, InP,GaN, AlN, sapphire, SiC, Si, or the like. The first semiconductor layer806, the active layers 808, and the second semiconductor layer 810 mayinclude various semiconductor materials, such as GaN, InGaN, (AlGaIn)P,(AlGaIn)AsP, (AlGaIn)AsN, (AlGaIn)Pas, (EuInGa)N, (AlGaIn)N, or thelike. In some embodiments, the first semiconductor layer 806 may be ann-type layer, and the second semiconductor layer 810 may be a p-typelayer. For example, the first semiconductor layer 806 may be an n-dopedGaN layer (e.g., doped with Si or Ge), and the second semiconductorlayer 810 may be a p-doped GaN layer (e.g., doped with Mg, Ca, Zn, orBe). The active layers 808 may include, for example, one or more GaNlayers, one or more InGaN layers, one or more AlInGaP layers, and thelike, which may form one or more heterostructures, such as one or morequantum wells or MQWs.

In some embodiments, the first wafer 802 may also include a bondinglayer 812. The bonding layer 812 may include various materials, such asa metal, an oxide, a dielectric, CuSn, AuTi, nanoporous metal, or thelike. In one example, the bonding layer 812 may include p-contactsand/or n-contacts (not shown). In some embodiments, other layers mayalso be included on the first wafer 802, such as a buffer layer betweenthe substrate 804 and the first semiconductor layer 806. The bufferlayer may include various materials, such as polycrystalline GaN or AlN.In some embodiments, a contact layer may be between the secondsemiconductor layer 810 and the bonding layer 812. The contact layer mayinclude any suitable material for providing an electrical contact to thesecond semiconductor layer 810 and/or the first semiconductor layer 806.

The first wafer 802 may be bonded to a wafer 803 that includes drivercircuits 811 and a bonding layer 813 as described above, via the bondinglayer 813 and/or the bonding layer 812. The bonding layer 812 and thebonding layer 813 may be made of the same material or differentmaterials. The bonding layer 812 and the bonding layer 813 may besubstantially flat. The first wafer 802 may be bonded to the wafer 803by various methods, such as metal-to-metal bonding, eutectic bonding,metal oxide bonding, anodic bonding, thermo-compression bonding,ultraviolet (UV) bonding, and/or fusion bonding.

As shown in FIG. 8B, the first wafer 802 may be bonded to the wafer 803with the p-side (e.g., the second semiconductor layer 810) of the firstwafer 802 facing down (i.e., toward the wafer 803). After bonding, thesubstrate 804 may be removed from the first wafer 802, and the firstwafer 802 may then be processed from the n-side. The processing mayinclude, for example, the formation of certain mesa shapes forindividual LEDs, as well as the formation of optical componentscorresponding to the individual LEDs.

FIGS. 9A-9D illustrates a method of hybrid bonding for arrays of LEDs,in accordance with one or more embodiments. The hybrid bonding maygenerally include wafer cleaning and activation, high-precisionalignment of contacts of one wafer with contacts of another wafer,dielectric bonding of dielectric materials at the surfaces of the wafersat room temperature, and metal bonding of the contacts by annealing atelevated temperatures. FIG. 9A shows a substrate 910 with passive oractive circuits 920 manufactured thereon. As described above withrespect to FIGS. 8A-8B, the substrate 910 may include, for example, asilicon wafer. The circuits 920 may include driver circuits for thearrays of LEDs and various electrical interconnects. A bonding layer mayinclude dielectric regions 940 and contact pads 930 connected to thecircuits 920 through electrical interconnects. The contact pads 930 mayinclude solid metal and/or nanoporous metal, for example, the metals mayinclude Cu, Ag, Au, Al, W, Mo, Ni, Ti, Pt, Pd, or the like. Dielectricmaterials in the dielectric regions 940 may include SiCN, SiO₂, SiN,Al₂O₃, HfO₂, ZrO₂, Ta₂O₅, or the like. The bonding layer may beplanarized and polished using, for example, chemical mechanicalpolishing, where the planarization or polishing may cause dishing (abowl like profile) in the contact pads. The surfaces of the bondinglayers may be cleaned and activated by, for example, an ion (e.g.,plasma) or a fast atom (e.g., Ar) beam 905. The activated surface may beatomically clean and may be reactive for formation of direct bondsbetween wafers when they are brought into contact, for example, at roomtemperature.

FIG. 9B illustrates a wafer 950 including an array of micro-LEDs 970fabricated thereon as described above with respect to, for example,FIGS. 7A-8B. The wafer 950 may be a carrier wafer and may include, forexample, GaAs, InP, GaN, AlN, sapphire, SiC, Si, or the like. Themicro-LEDs 970 may include an n-type layer, an active region, and ap-type layer epitaxially grown on the wafer 950. The epitaxial layersmay include various III-V semiconductor materials described above, andmay be processed from the p-type layer side to etch mesa structures inthe epitaxial layers, such as substantially vertical structures,parabolic structures, conic structures, or the like. Passivation layersand/or reflection layers may be formed on the sidewalls of the mesastructures. P-contacts 980 and n-contacts 982 may be formed in adielectric material layer 960 deposited on the mesa structures and maymake electrical contacts with the p-type layer and the n-type layers,respectively. Dielectric materials in the dielectric material layer 960may include, for example, SiCN, SiO₂, SiN, Al₂O₃, HfO₂, ZrO₂, Ta₂O₅, orthe like. The p-contacts 980 and the n-contacts 982 may include solidmetal and/or nanoporous metal, for example, the metals may include Cu,Ag, Au, Al, W, Mo, Ni, Ti, Pt, Pd, or the like. The top surfaces of thep-contacts 980, the n-contacts 982, and the dielectric material layer960 may form a bonding layer. The bonding layer may be planarized andpolished using, for example, chemical mechanical polishing, where thepolishing may cause dishing in the p-contacts 980 and the n-contacts982. The bonding layer may then be cleaned and activated by, forexample, an ion (e.g., plasma) or the fast atom (e.g., Ar) beam 915. Theactivated surface may be atomically clean and reactive for formation ofdirect bonds between wafers when they are brought into contact, forexample, at room temperature.

FIG. 9C illustrates a room temperature bonding process for bonding thedielectric materials in the bonding layers. For example, after thebonding layer that includes the dielectric regions 940 and the contactpads 930 and the bonding layer that includes the p-contacts 980, then-contacts 982, and the dielectric material layer 960 are surfaceactivated, the wafer 950 and the micro-LEDs 970 may be turned upsidedown and brought into contact with the substrate 910 and the circuitsformed thereon. In some embodiments, compression pressure 925 may beapplied to the substrate 910 and the wafer 950 such that the bondinglayers are pressed against each other. Due to the surface activation andthe dishing in the contacts, the dielectric regions 940 and thedielectric material layer 960 may be in direct contact because of thesurface attractive force, and may react and form chemical bonds betweenthem because the surface atoms may have dangling bonds and may be inunstable energy states after the activation. Thus, the dielectricmaterials in the dielectric regions 940 and the dielectric materiallayer 960 may be bonded together with or without heat treatment orpressure.

FIG. 9D illustrates an annealing process for bonding the contacts in thebonding layers after bonding the dielectric materials in the bondinglayers. For example, the contact pads 930 and the p-contacts 980 or then-contacts 982 may be bonded together by annealing at, for example,about 200-400° C. or higher. During the annealing process, heat 935(e.g., emitted by a laser) may cause the contacts to expand more thanthe dielectric materials (due to different coefficients of thermalexpansion), and thus may close the dishing gaps between the contactssuch that the contact pads 930 and the p-contacts 980 or the n-contacts982 may be in contact and may form direct metallic bonds at theactivated surfaces.

In some embodiments where the two bonded wafers include materials havingdifferent coefficients of thermal expansion (CTEs), the dielectricmaterials bonded at room temperature may help to reduce or preventmisalignment of the contact pads caused by the different thermalexpansions. In some embodiments, to further reduce or avoid themisalignment of the contact pads at a high temperature during annealing,trenches may be formed between micro-LEDs, between groups of micro-LEDs,through part or all of the substrate, or the like, before bonding.

After the micro-LEDs are bonded to the driver circuits, the substrate onwhich the micro-LEDs are fabricated may be thinned or removed, andvarious secondary optical components may be fabricated on the lightemitting surfaces of the micro-LEDs to, for example, extract, collimate,and redirect the light emitted from the active regions of themicro-LEDs. In one example, micro-lenses may be formed on themicro-LEDs, where each micro-lens may correspond to a respectivemicro-LED and may help to improve the light extraction efficiency andcollimate the light emitted by the micro-LED. In some embodiments, thesecondary optical components may be fabricated in the substrate or then-type layer of the micro-LEDs. In some embodiments, the secondaryoptical components may be fabricated in a dielectric layer deposited onthe n-type side of the micro-LEDs. Examples of the secondary opticalcomponents may include a lens, a grating, an antireflection (AR)coating, a prism, a photonic crystal, or the like.

FIG. 10 illustrates a LED array 1000 with secondary optical componentsfabricated thereon, in accordance with one or more embodiments. The LEDarray 1000 may be made by bonding an LED chip or wafer with a siliconwafer including electrical circuits fabricated thereon, using anysuitable bonding techniques described above with respect to, forexample, FIGS. 8A-9D. In the example shown in FIG. 10, the LED array1000 may be bonded using a wafer-to-wafer hybrid bonding technique asdescribed above with respect to FIG. 9A-9D. The LED array 1000 mayinclude a substrate 1010, which may be, for example, a silicon wafer.Integrated circuits 1020, such as LED driver circuits, may be fabricatedon the substrate 1010. The integrated circuits 1020 may be connected top-contacts 1074 and n-contacts 1072 of micro-LEDs 1070 through contactpads 1030, where the contact pads 1030 may form metallic bonds with thep-contacts 1074 and the n-contacts 1072. A dielectric layer 1040 on thesubstrate 1010 may be bonded to a dielectric layer 1060 through fusionbonding.

The substrate (not shown) of the LED chip or wafer may be thinned or maybe removed to expose the n-type layer 1050 of the micro-LEDs 1070.Various secondary optical components, such as a spherical micro-lens1082, a grating 1084, a micro-lens 1086, an antireflection layer 1088,and the like, may be formed in or on top of the n-type layer 1050. Forexample, spherical micro-lens arrays may be etched in the semiconductormaterials of the micro-LEDs 1070 using a gray-scale mask and aphotoresist with a linear response to exposure light, or using an etchmask formed by thermal reflowing of a patterned photoresist layer. Thesecondary optical components may also be etched in a dielectric layerdeposited on the n-type layer 1050 using similar photolithographictechniques or other techniques. For example, micro-lens arrays may beformed in a polymer layer through thermal reflowing of the polymer layerthat is patterned using a binary mask. The micro-lens arrays in thepolymer layer may be used as the secondary optical components or may beused as the etch mask for transferring the profiles of the micro-lensarrays into a dielectric layer or a semiconductor layer. The dielectriclayer may include, for example, SiCN, SiO₂, SiN, Al₂O₃, HfO₂, ZrO₂,Ta₂O₅, or the like. In some embodiments, the micro-LED 1070 may havemultiple corresponding secondary optical components, such as amicro-lens and an anti-reflection coating, a micro-lens etched in thesemiconductor material and a micro-lens etched in a dielectric materiallayer, a micro-lens and a grating, a spherical lens and an asphericallens, and the like. Three different secondary optical components areillustrated in FIG. 10 to show some examples of secondary opticalcomponents that can be formed on the micro-LEDs 1070, which does notnecessary imply that different secondary optical components are usedsimultaneously for every LED array.

FIGS. 11A and 11B are cross-sectional views of bonding contacts 1120 andelectrodes 1140 using nanoporous metal tips (i.e., tips 1125 and tips1145) as a hybrid interconnect, in accordance with one or moreembodiments. FIG. 11A shows a first body 1110 and a second body 1130prior to being adjoined, according to an embodiment. The first body 1110has a first surface 1115 with a plurality of contacts 1120 protrudingfrom the first surface 1115. In this embodiment, illustrated in FIG.11A, the contacts 1120 include nanoporous metal tips 1125 formed on topof a base layer 1127. The base layer 1127 may be made of a solid metal(e.g., Ti, Au, or other alloy). In some embodiments (not shown), thecontacts 1120 do not include nanoporous metal tips 1125. The nanoporousmetal tips 1125 may by formed on the contacts 1120 using fabricationmethods well known in the art. An example nanoporous metal tipfabrication method known to one skilled in the art is further describedin “Nanoporous interconnects” by Herman Oppermann, Lothar Dietrich,Matthias Klein, and Bernhard Wunderle and published by 3rd ElectronicsSystem Integration Technology Conference ESTC in September 2010, whichis hereby incorporated by reference in its entirety for all purposes.The first body 1110 may also include a backplane substrate with CMOSperiphery circuits. The first body 1110 may be a die or a wafer, asdescribed above with reference to FIGS. 8A-9D.

The second body 1130 may comprise a substrate on which an array of lightsources (e.g., an array of LEDs, such as an array of μLEDs) is formed.The array of light sources has a light-emission side and a side oppositethe light-emission side. The second body 1130 has a second surface 1135that faces the first surface 1115 of the first body 1110. In oneexample, the second surface 1135 is the side opposite the light-emissionside. The second surface 1135 has a plurality of electrodes 1140protruding from the second surface 1135 that are connected to electricalcomponents or conductive traces in the second body 1130. In thisembodiment, illustrated in FIG. 11A, the electrodes 1140 includenanoporous metal tips 1145 formed on top of a base layer 1147. The baselayer 1147 may be made of a solid metal (e.g., Au). In some embodiments(not shown), the electrodes 1140 do not include nanoporous metal tips1145. In one example, the first surface 1115 and/or the second surface1135 may include a top insulation layer or a top passivation layer. Thesecond body 1130 may be a die or a wafer separate from the first body1110, as described above with reference to FIGS. 8A-9D.

As shown in FIG. 11A, the contacts 1120 and the corresponding electrodes1140 are not in contact or adjoined, but are aligned such that if eitherthe first surface 1115 or the second surface 1135 were moved towards theother along a linear path, each contact 1120 would engage with acorresponding electrode 1140. In another embodiment, the first body 1110comprises one or more LEDs and the second body 1130 comprises a circuitto operate the one or more LEDs. The LEDs may have a size of less than100 μm (i.e., the LEDs may be micro-LEDs).

FIG. 11B illustrates the first body 1110 and the second body 1130 bondedusing a laser beam 1150, according to one embodiment. In one embodiment,the laser beam 1150 may be applied to at least one of the contacts 1120and the electrodes 1140 at a time. In some embodiments, the laser beam1150 may be projected onto a subset of the contacts 1120 and theelectrodes 1140 at a time. In one embodiment, the laser beam 1150 may beapplied to the first body 1110. In some embodiments, the laser beam 1150may be applied to the second body 1130. The laser beam 1150 may bescanned across either the first body 1110 or the second body 1130. Asthe contacts and the electrodes are exposed to the laser beam 1150, thenanoporous metal tips (i.e., the tips 1125 and the tips 1145,respectively) melt and form bonding metal 1160. The bonding metal 1160is the melted and solidified nanoporous metal tips 1125, 1145. Thebonding metal 1160 establishes an interconnection between the contactsand the electrodes and bonds the first body 1110 to the second body1130. In one example, the laser beam 1150 emits light with a wavelengthof 360 nm (i.e., an ultraviolet ray) and forms a spot of 1.5-2 mm on thefirst body 1110. In this example, a whole 3×4 mm chip may be bonded in afew seconds. In another example, the laser beam 1150 emits light with awavelength of below 360 nm and forms a spot of 1 mm.

In one embodiment, the interconnection formed between the contacts 1120and the electrodes 1140 (i.e., where bonding metal 1160 is formed) mayconnect the electrodes of the light sources of the second body 1130 withthe CMOS periphery circuits in the backplane substrate of the first body1110. The CMOS periphery circuits may supply electrical current to thelight sources through the interconnection. The number of theinterconnections established may be less than the number of lightsources in the array of light sources as one interconnection may be usedto enable sending data to operate multiple light sources.

FIG. 12 is a flowchart illustrating a process for interconnecting afirst body to a second body via contact and electrodes using nanoporousmetal tips, in accordance with one or more embodiments. The process mayinclude different or additional steps than those described inconjunction with FIG. 12 in some embodiments or perform steps indifference orders than the order described in conjunction with FIG. 12.

As illustrated in FIGS. 11A and 11B, the first body of the interconnect(i.e., the first body 1110) on which contacts protrude from a firstsurface is positioned 1210 relative to the second body (i.e., the secondbody 1130) to align the contacts with corresponding electrodes on thesecond body. The electrodes protrude from a second surface on the secondbody. The second surface faces the first surface. The contacts, theelectrodes, or both comprise nanoporous metal tips. After the first bodyand the second body are positioned, the first body approaches 1220 thesecond body such that the position of the first body is moved towardsthe second body until the contacts and the electrodes are separated byless than a predetermined distance. The contacts and the electrodes bond1230 establishing an interconnect between the first body and the secondbody. The bond takes place by melting and solidifying the nanoporousmetal tips.

In some embodiments, the contacts and the electrodes are mounted to theopposite bodies of the interconnect compared to the above description.For example, the contacts are formed on the second body (specifically,on the second surface of the second body) and the electrodes are formedon the first body (specifically, on the first surface of the firstbody).

The methods, systems, and devices discussed above are examples. Variousembodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods described may be performed in an order different from thatdescribed, and/or various stages may be added, omitted, and/or combined.Also, features described with respect to certain embodiments may becombined in various other embodiments. Different aspects and elements ofthe embodiments may be combined in a similar manner. Also, technologyevolves and, thus, many of the elements are examples that do not limitthe scope of the disclosure to those specific examples.

What is claimed is:
 1. A method comprising: positioning a first bodyrelative to a second body to align contacts protruding from a firstsurface of the first body with electrodes protruding from a secondsurface of the second body facing the first surface, wherein at leastone of the contacts and the electrodes comprises nanoporous metal tips;approaching the first body and the second body so that the contacts andthe electrodes are separated by less than a predetermined distance afterpositioning the first body; and bonding the contacts with correspondingelectrodes by melting and solidifying the nanoporous metal tips afterapproaching the first body and the second body by heating at least oneof the contacts and the electrodes with a laser beam to melt thenanoporous metal.
 2. The method of claim 1, wherein the laser beam isprojected onto a subset of the contacts and the electrodes at a time. 3.The method of claim 1, wherein the nanoporous metal tips are nanoporousgold tips.
 4. The method of claim 1, wherein each of the contacts andeach of the electrodes further comprise a solid metal base on the firstbody or the second body.
 5. The method of claim 1, wherein one of thefirst body and the second body comprises a light emitting diode (LED)having a size that is less than 100 micrometers (μm) and the other ofthe first body and the second body comprises a circuit to operate theLED.
 6. An electronic device manufactured by a method comprising:positioning a first body relative to a second body to align contactsprotruding from a first surface of the first body with electrodesprotruding from a second surface of the second body facing the firstsurface, wherein at least one of the contacts and the electrodescomprises nanoporous metal tips; approaching the first body and thesecond body so that the contacts and the electrodes are separated byless than a predetermined distance after positioning the first body; andbonding the contacts with corresponding electrodes by melting andsolidifying the nanoporous tips after approaching the first body and thesecond body by heating at least one of the contacts and the electrodeswith a laser beam to melt the nanoporous metal.
 7. The electronic deviceof claim 6, wherein the laser beam is projected onto a subset of thecontacts and the electrodes at a time.
 8. The electronic device of claim6, wherein the nanoporous metal tips are nanoporous gold tips.
 9. Theelectronic device of claim 6, wherein each of the contacts and each ofthe electrodes further comprise a solid metal base on the first body orthe second body.
 10. The electronic device of claim 6, wherein one ofthe first body and the second body comprises a light emitting diode(LED) having a size that is less than 100 micrometers (μm) and the otherof the first body and the second body comprises a circuit to operate theLED.